Uncertainty in parameter estimation on a data set on dechlorination of tetrachloroethylene in batch experiments.

Abstract

A model was developed to investigate the results of batch experiments performed with a dechlorinating microbial assemblage over a range of initial PCE concentrations. Experimental results revealed that with increasing PCE concentrations, dechlorination was incomplete and stalled at initial PCE concentrations higher than 0.5 mM. Moreover, results of triplicate batch experiments did not always show the same pattern. The constructed model included kinetic and thermodynamic constraints for dechlorination, fermentation, and biomass growth. Dechlorination rate parameters were estimated for one batch experiment by fitting the chlorinated ethene concentrations with the SCEM-UA algorithm. Application of the obtained parameters to other batch experiments did not result in a good fit with the experimental results. The model showed a high sensitivity for the rate of competitive inhibition between chlorinated ethenes, reaction rates of electron donor fermentation related to electron donor consumption by competing processes and initial biomass concentrations. A slight change in initial conditions will result in very different chlorinated ethene concentrations. This leads to the conclusion that in field conditions, changes in initial conditions can prevent biological processes to proceed at maximum degradation rates.